More checking for unpack of tampered Elf_Phdr

https://github.com/upx/upx/issues/562
	modified:   p_elf_enum.h
	modified:   p_lx_elf.cpp

src/p_elf_enum.h

@@ -92,6 +92,7 @@
         PT_INTERP  = 3,         /* Name of program interpreter */
         PT_NOTE    = 4,         /* Auxiliary information (esp. OpenBSD) */
         PT_PHDR    = 6          /* Entry for header table itself */
+        , PT_NUM   = 8          /* Number of defined types in low range */
         , PT_GNU_STACK = 0x6474e551      /* Indicates stack executability */
     };